SED(1) User Commands SED(1)

NAME

sed - stream editor

SYNOPSIS

sed [-Ealnr] command [file ...]
sed [-Ealnr] [-e command] [-f command_file] [-I[extension] |
-i[extension]] [file ...]

DESCRIPTION

The sed utility reads the specified files, or the standard input if
no files are specified, modifying the input as specified by a list of
commands. The input is then written to the standard output.

A single command may be specified as the first argument to sed.
Multiple commands may be specified by using the -e or -f options.
All commands are applied to the input in the order they are specified
regardless of their origin.

The following options are available:

-E Interpret regular expressions as extended (modern) regular
expressions rather than basic regular expressions (BRE's).
The regex(7) manual page fully describes both formats.

-a The files listed as parameters for the ``w'' functions are
created (or truncated) before any processing begins, by
default. The -a option causes sed to delay opening each file
until a command containing the related ``w'' function is
applied to a line of input.

-e command
Append the editing commands specified by the command argument
to the list of commands.

-f command_file
Append the editing commands found in the file command_file to
the list of commands. The editing commands should each be
listed on a separate line.

-I[extension]
Edit files in-place, saving backups if extension was
specified. It is not recommended to omit saving backups when
in-place editing files, as you risk corruption or partial
content in situations where disk space is exhausted, etc.

Note that in-place editing with -I still takes place in a
single continuous line address space covering all files,
although each file preserves its individuality instead of
forming one output stream. The line counter is never reset
between files, address ranges can span file boundaries, and
the ``$'' address matches only the last line of the last file.
(See Sed Addresses . ) That can lead to unexpected results in
many cases of in-place editing, where using -i is desired.

-i[extension]
Edit files in-place similarly to -I, but treat each file
independently from other files. In particular, line numbers
in each file start at 1, the ``$'' address matches the last
line of the current file, and address ranges are limited to
the current file. (See Sed Addresses . ) The net result is as
though each file were edited by a separate sed instance.

-l Make output line buffered.

-n By default, each line of input is echoed to the standard
output after all of the commands have been applied to it. The
-n option suppresses this behavior.

-r Same as -E for compatibility with GNU sed.

The form of a sed command is as follows:

[address[,address]]function[arguments]

Whitespace may be inserted before the first address and the function
portions of the command.

Normally, sed cyclically copies a line of input, not including its
terminating newline character, into a pattern space, (unless there is
something left after a ``D'' function), applies all of the commands
with addresses that select that pattern space, copies the pattern
space to the standard output, appending a newline, and deletes the
pattern space.

Some of the functions use a hold space to save all or part of the
pattern space for subsequent retrieval.

If an input file is growing while sed is running, the ``$'' address
match may be unreliable.

Sed Addresses
An address is not required, but if specified must have one of the
following formats:

+o a number that counts input lines cumulatively across input
files (or in each file independently if a -i option is in
effect);

+o a dollar (``$'') character that addresses the last line of
input (or the last line of the current file if a -i option was
specified);

+o a context address that consists of a regular expression
preceded and followed by a delimiter. The closing delimiter
can also optionally be followed by the ``I'' character, to
indicate that the regular expression is to be matched in a
case-insensitive way.

A command line with no addresses selects every pattern space.

A command line with one address selects all of the pattern
spaces that match the address.

A command line with two addresses selects an inclusive range.
This range starts with the first pattern space that matches
the first address. The end of the range is the next following
pattern space that matches the second address. If the second
address is a number less than or equal to the line number
first selected, only that line is selected. The number in the
second address may be prefixed with a (``+'') to specify the
number of lines to match after the first pattern. In the case
when the second address is a context address, sed does not re-
match the second address against the pattern space that
matched the first address. Starting at the first line
following the selected range, sed starts looking again for the
first address.

Editing commands can be applied to non-selected pattern spaces
by use of the exclamation character (``!'') function.

Sed Regular Expressions
The regular expressions used in , by default, are basic regular
expressions (BREs, see regex(7) for more information), but extended
(modern) regular expressions can be used instead if the -E flag is
given. In addition, sed has the following two additions to regular
expressions:


1. In a context address, any character other than a backslash
(``\'') or newline character may be used to delimit the
regular expression. The opening delimiter needs to be
preceded by a backslash unless it is a slash. For example,
the context address \xabcx is equivalent to /abc/ . Also,
putting a backslash character before the delimiting character
within the regular expression causes the character to be
treated literally. For example, in the context address
\xabc\xdefx , the RE delimiter is an ``x'' and the second
``x'' stands for itself, so that the regular expression is
``abcxdef''.


2. The escape sequence \n matches a newline character embedded in
the pattern space. You cannot, however, use a literal newline
character in an address or in the substitute command.

One special feature of sed regular expressions is that they
can default to the last regular expression used. If a regular
expression is empty, i.e., just the delimiter characters are
specified, the last regular expression encountered is used
instead. The last regular expression is defined as the last
regular expression used as part of an address or substitute
command, and at run-time, not compile-time. For example, the
command ``/abc/s//XXX/'' will substitute ``XXX'' for the
pattern ``abc''.

Sed Functions
In the following list of commands, the maximum number of permissible
addresses for each command is indicated by [0addr], [1addr], or
[2addr], representing zero, one, or two addresses.

The argument text consists of one or more lines. To embed a newline
in the text, precede it with a backslash. Other backslashes in text
are deleted and the following character taken literally.

The ``r'' and ``w'' functions take an optional file parameter, which
should be separated from the function letter by white space. Each
file given as an argument to sed is created (or its contents
truncated) before any input processing begins.

The ``b'', ``r'', ``s'', ``t'', ``w'', ``y'', ``!'', and ``:''
functions all accept additional arguments. The following synopses
indicate which arguments have to be separated from the function
letters by white space characters.

Two of the functions take a function-list. This is a list of sed
functions separated by newlines, as follows:

{ function
function
...
function
}

The ``{'' can be preceded by white space and can be followed by white
space. The function can be preceded by white space. The terminating
``}'' must be preceded by a newline or optional white space.


[2addr] function-list
Execute function-list only when the pattern space is selected.


[1addr]a\

text Write text to standard output immediately before each attempt
to read a line of input, whether by executing the ``N''
function or by beginning a new cycle.


[2addr]b[label]
Branch to the ``:'' function with the specified label. If the
label is not specified, branch to the end of the script.


[2addr]c\

text Delete the pattern space. With 0 or 1 address or at the end
of a 2-address range, text is written to the standard output.


[2addr]d
Delete the pattern space and start the next cycle.


[2addr]D
Delete the initial segment of the pattern space through the
first newline character and start the next cycle.


[2addr]g
Replace the contents of the pattern space with the contents of
the hold space.


[2addr]G
Append a newline character followed by the contents of the
hold space to the pattern space.


[2addr]h
Replace the contents of the hold space with the contents of
the pattern space.


[2addr]H
Append a newline character followed by the contents of the
pattern space to the hold space.


[1addr]i\

text Write text to the standard output.


[2addr]l
(The letter ell.) Write the pattern space to the standard
output in a visually unambiguous form. This form is as
follows:


backslash
\\

alert \a

form-feed
\f

carriage-return
\r

tab \t

vertical tab
\v

Nonprintable characters are written as three-digit octal
numbers (with a preceding backslash) for each byte in the
character (most significant byte first). Long lines are
folded, with the point of folding indicated by displaying a
backslash followed by a newline. The end of each line is
marked with a ``$''.


[2addr]n
Write the pattern space to the standard output if the default
output has not been suppressed, and replace the pattern space
with the next line of input.


[2addr]N
Append the next line of input to the pattern space, using an
embedded newline character to separate the appended material
from the original contents. Note that the current line number
changes.


[2addr]p
Write the pattern space to standard output.


[2addr]P
Write the pattern space, up to the first newline character to
the standard output.


[1addr]q
Branch to the end of the script and quit without starting a
new cycle.


[1addr]r file
Copy the contents of file to the standard output immediately
before the next attempt to read a line of input. If file
cannot be read for any reason, it is silently ignored and no
error condition is set.


[2addr]s/regular expression/replacement/flags
Substitute the replacement string for the first instance of
the regular expression in the pattern space. Any character
other than backslash or newline can be used instead of a slash
to delimit the RE and the replacement. Within the RE and the
replacement, the RE delimiter itself can be used as a literal
character if it is preceded by a backslash.

An ampersand (``&'') appearing in the replacement is replaced
by the string matching the RE. The special meaning of ``&''
in this context can be suppressed by preceding it by a
backslash. The string ``\#'', where ``#'' is a digit, is
replaced by the text matched by the corresponding
backreference expression (see regex(7)) .

A line can be split by substituting a newline character into
it. To specify a newline character in the replacement string,
precede it with a backslash.

The value of flags in the substitute function is zero or more
of the following:

N Make the substitution only for the N'th occurrence of the
regular expression in the pattern space.

g Make the substitution for all non-overlapping matches of the
regular expression, not just the first one.

p Write the pattern space to standard output if a replacement
was made. If the replacement string is identical to that
which it replaces, it is still considered to have been a
replacement.

w file Append the pattern space to file if a replacement was made.
If the replacement string is identical to that which it
replaces, it is still considered to have been a replacement.

I Match the regular expression in a case-insensitive way.


[2addr]t [label]
Branch to the ``:'' function bearing the label if any
substitutions have been made since the most recent reading of
an input line or execution of a ``t'' function. If no label
is specified, branch to the end of the script.


[2addr]w file
Append the pattern space to the file.


[2addr]x
Swap the contents of the pattern and hold spaces.


[2addr]y/string1/string2/
Replace all occurrences of characters in string1 in the
pattern space with the corresponding characters from string2.
Any character other than a backslash or newline can be used
instead of a slash to delimit the strings. Within string1 and
string2, a backslash followed by any character other than a
newline is that literal character, and a backslash followed by
an ``n'' is replaced by a newline character.


[2addr]!function

[2addr]!function-list
Apply the function or function-list only to the lines that are
not selected by the address(es).


[0addr]:label
This function does nothing; it bears a label to which the
``b'' and ``t'' commands may branch.


[1addr]=
Write the line number to the standard output followed by a
newline character.


[0addr]
Empty lines are ignored.


[0addr]#
The ``#'' and the remainder of the line are ignored (treated
as a comment), with the single exception that if the first two
characters in the file are ``#n'', the default output is
suppressed. This is the same as specifying the -n option on
the command line.

ENVIRONMENT

The COLUMNS,LANG,LC_ALL,LC_CTYPE and LC_COLLATE environment variables
affect the execution of sed as described in environ(7).

EXIT STATUS

The sed utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

awk(1), ed(1), grep(1), regex(7)

STANDARDS

The sed utility is expected to be a superset of the IEEE Std 1003.2
(``POSIX.2'') specification.

The -E, I , a and -i options, the prefixing ``+'' in the second
member of an address range, as well as the ``I'' flag to the address
regular expression and substitution command are non-standard
extensions and may not be available on other operating systems.

HISTORY

A sed command, written by L. E. McMahon, appeared in Version 7 AT&T
UNIX.

AUTHORS

"Diomidis D. Spinellis" <dds@FreeBSD.org>

BUGS

Multibyte characters containing a byte with value 0x5C (ASCII `\')
may be incorrectly treated as line continuation characters in
arguments to the ``a'', ``c'' and ``i'' commands. Multibyte
characters cannot be used as delimiters with the ``s'' and ``y''
commands.

August 21, 2020 SED(1)